While conventional electronics is based on the charge of electrons, spintronics is based on exploiting the additional spin degree of freedom (in addition to the charge degree of freedom), which offers advantages for electronics and computing applications.
Controlling spin transport at the nanoscale is of particular interest because of the possibility to utilize interesting effects that emerge only at this scale. The ability to filter a highly spin-polarized current governed by electrons of a single spin type is of central importance for the efficient operation of spin-based devices. Methods for achieving spin-polarized currents at the length scale of several microns down to tenths of a micron include careful fabrication of structures based on half-metals, lateral separation of spin currents by magnetic field and the use of intrinsic effects as spin-orbit interactions.
There is a need in the art in novel nanoscale structures for spintronic components at the nanoscale, having an enhanced spin-filtering effect characterized by both high spin-polarization of the transmitted electronic current (95-100% of the current is spin polarized) and very large spin-current density (˜1011 A cm−2) so as to enable use of such structures in realization of atomic-scale spintronic applications, including very high magnetoresistance effects and significant spin-torque transfer.
As indicated above, spin-polarized currents can be achieved by careful fabrication of half-metals based structures, lateral separation of spin currents by magnetic field, and the use of intrinsic effects as spin-orbit interactions. However, when the system size is decreased toward the nanoscale, achieving high spin polarization has shown to become increasingly challenging. Alternative schemes explored at the nanoscale include atomic-scale ferromagnetic spin-valves based on atomic and molecular junctions. Yet, to date such experiments have indicated limited spin polarization, resulting in magnetoresistance values of a few tens of percent at the most.